Conductive laminate

ABSTRACT

A conductive laminate comprising a substrate (2), an intermedaite layer (3) provided on the substrate (2) and made of an amorphous metallic or semi-metallic oxide, and a transparent conductive layer (4) provided on the intermediate layer (3) and made of a crystalline metal or metallic oxide. The material of the conductive layer (4) is a member selected from among Au, Pd, Cr, Ni, SnO 2 , In 2  O 3 , ZnO, TiO 2 , CdO, CdO--SnO 2 , and ITO. The material of the intermediate layer (3) is a member selected from among SnO 2 , ITO, SiO 2  and Al 2  O 3 . The thickness of the conductive layer (4) is 200 to 10,000 Å. The thickness of the intermediate layer (3) is 80 to 300 Å.

DESCRIPTION

1. Technical Field

The present invention relates to a conductive laminate, and morespecifically to a conductive laminate suitably used in display devicessuch as a liquid crystal display device.

2. Background Art

Transparent conductive films and transparent conductive laminates arewidely used in the electric and electronic fields including thoseconcerning not only electrodes for liquid crystal display devices,electroluminescence display devices, and photoconductive photosensitiveelements, but also cathode ray tubes, electrostatic shielding layers inthe window portions of various measurement apparatuses, antistaticlayers, and heating elements. Of them, transparent conductive filmshaving selective light transmittance has an infrared ray reflectionproperty and are utilized as window materials in collectors forutilization of solar energy and in buildings. A transparent electrodenever fail to be used in various solid display devices wherein anelectroluminescence, liquid crystal, plasma, or ferroelectric substanceis used, which have been developed as substitutes for cathode ray tubeswith the progress of information processing technologies. Besides, afilm having transparency and electroconductivity is required in newphotoelectric elements and recording materials utilizing interaction orinterconversion between electric and optical signals, which are regardedas useful in the information processing technique from now on. Thesetransparent conductive layers can be utilized also in condensation-proofwindow glass used in automobiles, airplanes, etc., in antistatic filmsfor polymers, glass, etc., and in transparent heat-insulating windowsfor prevention of dissipation of solar energy. In liquid crystal,electroluminescence, plasma, electrochromic, and fluorescence displaydevices, etc., a demand particularly for high-quality picture elementdisplay has recently increased. Under these circumstances, there hasbeen a proposal according to which the portion of a picture element andthe signal input line are formed with an electrode made of a transparentconductive layer and a low resistance electrode, respectively, to attainimprovements in the display speed of the picture element and the qualityof images.

On the other hand, patterning of the transparent conductive layer of aconductive laminate in display devices such as a liquid crystal displaydevice is generally effected by photoetching, which includes the step ofimmersion in an alkali to remove a photoresist remaining on theconductive laminate and the step of washing the surfaces of theconductive laminate with an acid after patterning. In these steps,cracking or local peeling sometimes occurs in the transparent conductivelayer, leading to a grave defect to the conductive laminate as will bedescribed later.

Although the cause of the above-mentioned phenomenon has not beenelucidated, it is believed to be due to the action of an internal stresssetting up in the transparent conductive layer because of a differencein thermal expansion coefficient between the substrate and thetransparent conductive layer.

Specifically, in deposition of the transparent conductive layer on thesubstrate by vacuum evaporation, the substrate is heated at atemperature of 300° C. or lower to raise the degree of oxidation of thedeposited layer for the purpose of improving the transparency andelectroconductivity thereof. The thermal expansion coefficient of thesubstrate is 5.5×10⁻⁵ cm/cm/°C. in the case of polyether-sulfone (PES)and 1.5×10⁻⁵ cm/cm/°C. in the case of polyethylene terephthalate (PET),while the thermal expansion coefficients of, for example, indium oxide(In₂ O_(x), x≦3) and indium-tin oxide (ITO) are of the order of 10⁻⁶cm/cm/°C. Thus, there is a large difference in thermal expansioncoefficient between the substrate and the transparent conductive layer.Therefore, it is believed that, at room temperature, an internal stressmay set up in the transparent conductive layer due to shrinkage of thesubstrate, and corrosion may progress in an acid or alkali solution withthe aid of the internal stress to cause cracking or local peeling.

On the other hand, there has been proposed a two-layer transparentconductive film having an indium oxide film formed on a transparentsubstrate and a tin oxide film subsequently formed thereon (JapanesePatent Laid-Open No. 22,789/1977). Use of this transparent conductivefilm as a transparent electrode plate in, for example, an element of aliquid crystal display device aims at maintaining its transparency andelectroconductivity after a heat treatment which is performed by heatingat 500° C. or higher in securing sealing of a panel with a glass sealingmaterial.

This transparent conductive film involves problems that the resistanceof the film against the above-mentioned acid or alkali is reduced whenpinholes or cracks are present in the tin oxide layer; that patterningis difficult because of grave side etching due to a large difference insolubility between the indium oxide layer and the tin oxide layer; andthat provision of the indium oxide layer on the side of the substrateprovides no satisfactory acid or alkali resistance so that cracking orpeeling is liable to occur.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a conductive laminatehaving a sufficient acid and alkali resistance, which solves theabove-mentioned problems involved in conventional conductive laminates.

Specifically, the present invention provides a conductive laminatecomprising a substrate and a transparent conductive layer formed thereonand made of a crystalline metal or metallic oxide, characterized bycomprising an intermediate layer provided between the substrate and thetransparent conductive layer and made of an amorphous metallic orsemimetallic oxide.

In the present invention, usable materials of the substrate includeinorganic materials such as quartz glass, soda glass, potassium glass,and other glass; and organic polymer materials such as polyethyleneterephthalate (PET), polyethylene naphthalate, polyhexamethylenediamide,poly-γ-butyramide, poly-m-xylenediamine terephthalamide, aromaticpolyesters or aromatic polyester carbonates mainly prepared frombisphenol A, its halogenated derivative and an acryl dichloride,polyamide copolymers of m-phenylenediamine, isophthalic acid andterephthalic acid, polycarbonate, polypropylene, polyimides, polyamides,imido-polybenzimidazole, polyethersulfone (PES), polyether ether ketone,polysulfone, polyether imide, and triacetylcellulose. They may have apolarizing filter function. When stretching is necessary in themanufacture of them, either monoaxial or biaxial stretching may beeffected.

A plurality of polymer resins may be laminated or mixed on the surfaceopposite the surface of the substrate on which the intermediate layerand the transparent conductive layer are formed. For example, a coat ofSaran which is a polyvinylidene chloride resin may be superposed as abarrier layer for prevention of water permeation. A layer having otherfunctions such as prevention of reflection or scratch, or a layer of agas barrier resin may also be laminated.

When a polyvinylidene chloride material, for example, Saran Latex(registered trademark) L 520 or L 511 manufactured by Asahi ChemicalIndustry Co., Ltd., is applied on a polymer film substrate by a wirebar, a very high water-permeation-proof effect is secured.

Conditions of such coating may include, for example, use of a PET or PESfilm of 100 μm in thickness as the substrate, dilution of a Saran Latexstock solution (solids content: 48%) with water 1.0 to 3-fold, a wetwire bar coating thickness of 3 to 60 μm, a carrying rate of 100 to 200m/min, drying with hot air of 90° to 140° C., and a dry coating layerthickness of 1 to 30 μm.

The thickness of the substrate is preferably 0.2 to 20 mm in the case ofa glass substrate and 100 μm in the case of an organic polymersubstrate.

The transparent conductive layer is made of a crystalline material,which is preferably a thin metallic film of Au, Pd, Cr, or Ni; or a filmof a metallic oxide such as SnO₂, In₂ O₃, ZnO, TiO₂, CdO, CdO-SnO₂, ITO(indium tin oxide) as mentioned above, or the like. The thickness of thetransparent conductive layer is preferably 200 to 10,000 Å, particularlypreferably 200 to 1,000 Å. Indium oxide (In₂ O₃) and ITO having a tincontent (the proportion of tin relative to the total of tin and indium,Sn/Sn+In; the same will apply hereinafter) of less than 7% areespecially preferred, and those containing Cd, Zn, Al, or the like inaddition to the above-mentioned component can also be used.

The intermediate layer provided between the substrate and thetransparent conductive layer is made of an amorphous material, which ispreferably one containing a component selected from among not only ITOand tin oxide (SnO₂) but also insulating metallic or semi-metallicoxides such as silicon oxide (SiO₂) and aluminum oxide (Al₂ O₃). Tinoxide (SnO₂) and ITO having a tin content of 7% or more, preferably 10%or more, are especially preferred. The thickness of the intermediatelayer is preferably 80 Å or more, particularly preferably 80 to 300 Å.Formation of the intermediate layer is performed by reactive vacuumevaporation and deposition or reactive sputtering.

BRIEF DESCRIPTION OF DRAWINGS

All the drawings will illustrate examples of the present invention.

FIG. 1 is a cross-sectional view of a conductive laminate.

FIG. 2 is a graph showing a relationship between the tin content and thesheet resistance of a transparent conductive layer.

FIG. 3 is a graph showing a relationship between the thickness and thechanges in the sheet resistance of a tin oxide intermediate layer whichis caused by immersion in an acid.

FIG. 4 is a rough cross-sectional view of a vacuum deposition apparatusused for film formation.

FIG. 5 is a perspective view of a gas electric discharge apparatusprovided in the vacuum deposition apparatus.

FIG. 6 is a cross-sectional view of another conductive laminate.

FIG. 7 is a cross-sectional view of a liquid crystal display device.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be illustrated with reference to theattached drawings.FIG. 1 shows a cross-sectional view of a conductivelaminate 1 according to the present invention, which has a substrate 2,and an intermediate layer 3 and a transparent conductive layer 4deposited thereon in sequence. A layer made of an inorganic substancesuch as Al₂ O₃ for the purpose of improving the light transmittance bymeans of, for example, a light interference effect, a layer made of apolymer substance, or other additional intermediate layer (which may becrystalline) may be provided between the intermediate layer and thetransparent conductive layer.

An example in which indium oxide or ITO is used as the material of thetransparent conductive layer will now be described.

The process of embodying the present invention will be first described.In the following tests, PES or monoaxially or biaxially stretched PEThaving a thickness of 100 μm was used as the substrate, while formationof a intermediate layer and a transparent conductive layer was performedby reactive vacuum evaporation and deposition (source of evaporation:In, In-Sn, In₂ O₃, ITO) or reactive sputtering (target: In, In-Sn, In₂O₃, ITO).

Preparatory Test 1

As to a conventional conductive laminate having no intermediate layer, arelationship between the tin content and the sheet resistance of atransparent conductive layer was examined. The film formationtemperature (temperature of a substrate in vacuum deposition) was 10° to200° C., and the thickness of the resulting film was 600 Å.

The test results are shown in FIG. 2.

The sheet resistance R remains substantially constant at 100 Ω/□ up to atin content of 7 atomic %, begins to gradually increase when it exceeds7 atomic %, and reaches 170 Ω/□ at a tin content of 10 atomic %. Whenthe tin content exceeds 10 atomic %, the sheet resistance begins toincrease rapidly, with the result that a difficulty may be encounteredin controlling the sheet resistance on a given level while a lowresistance value cannot be secured. Accordingly, the tin content of thetransparent conductive layer is desired to be 7 atomic % or lower.

Preparatory Test 2

(i) As to a conventional conductive laminate having no intermediatelayer, the acid resistance was examined based on a relationship betweenthe temperature of the substrate in film formation (film formationtemperature) and a change in the sheet resistance before and afterimmersion in an acid. The film formation temperature was in a range offrom 10° to 200° C. The transparent conductive layer was made of indiumoxide or ITO having a tin content of up to 10 atomic %, and had athickness of 500 Å. The acid was 0.05N hydrochloric acid. The liquidtemperature was 20° C., and the immersion time was 30 minutes.

When the sheet resistances before and after immersion in the acid areexpressed by R₀ and R, respectively, the film formation temperature forproviding R/R ₀ ≦2 (R/R₀ is desired to be close to 1 and at most 2.0)varies depending on the tin content of the transparent conductive layeras shown in the following Table 1.

                  TABLE 1                                                         ______________________________________                                                     Necessary film                                                   Tin content  formation temperature                                            ______________________________________                                        0 at. %       90° C. or higher                                         1 at. %      130° C. or higher                                         3 at. %      140° C. or higher                                         5 at. %      150° C. or higher                                         8 at. %      180° C. or higher                                         10 at. %     200° C. or higher                                         ______________________________________                                    

In the table, at. % stands for atomic % (the same will applyhereinafter).

It can be understood from the table that the film formation temperaturemust be higher with a higher tin content of the transparent conductivelayer in order to provide a value of R/R₀ of 2.0 or less.

Although the value of R/R₀ was 2.0 or less under the conditions listedin Table 1, cracks were formed in the transparent conductive layer afterimmersion in an acid. Thus, the acid resistance was not satisfactory. Itwas found that transparent conductive layers prepared at necessary filmformation temperatures as listed in Table 1 included crystalline matterssince diffraction patterns were observed in the X-ray diffraction test.In view of this, it is effective to make the transparent conductivelayer crystalline for the purpose of at least attaining R/R₀ of ≦2.0 inrespect of acid resistance.

(ii) While keeping the tin content of the transparent conductive layerat 3 atomic %, a relationship between the film formation temperature andthe alkali resistance was examined to obtain the results listed in Table2. The alkali resistance was evaluated by a change in the sheetresistance before immersion (R₀) and after immersion (R) in a 5 wt. %aqueous KOH solution (20° C.) for 10 minutes and a change in the surfacestate.

In the table, o, Δ, and x stand for the respective states as mentionedbelow (the same will apply hereinafter).

o: R/R₀ ≦2.0, neither cracking nor peeling was observed.

Δ: R/R₀ ≦2.0, cracking occurred but no peeling was observed.

x: R/R₀ >2.0, cracking and peeling occurred.

                  TABLE 2                                                         ______________________________________                                        Film                           X-ray                                          formation  Acid       Alkali   diffraction                                    temperature                                                                              resistance resistance                                                                             test                                           ______________________________________                                         50° C.                                                                           x          o        amorphous                                       80° C.                                                                           x          Δ  amorphous and                                                                 crystalline                                    140° C.                                                                           Δ    Δ  crystalline                                    150° C.                                                                           Δ    Δ                                                 180° C.                                                                           Δ    x                                                       200° C.                                                                           Δ    x                                                       ______________________________________                                    

In the case of film formation temperatures higher than the necessaryfilm formation temperature (tin: 3 atomic %; 140° C. or higher),cracking occurred in respect of acid resistance, but R/R₀ ≦2.0. Inrespect of alkali resistance, as the temperature was higher, surfacecracking caused by immersion in an alkali turned out more notablesometimes with peeling, and R/R₀ exceeded 2.0 when the temperature ishigher than a given one.

It is believed that occurrence of cracking in a transparent conductivelayer during immersion in an acid or alkali in the case of higher filmformation temperatures might have been induced by an increased internalstress setting up in the transparent conductive layer due to adifference in thermal expansion coefficient between a substrate and thetransparent conductive layer.

As described above, no conductive laminates obtained by directly forminga transparent conductive layer on a substrate could satisfy both theacid and alkali resistances. In Table 2, transparent conductive layersformed at film formation temperatures of 140° C. or higher showedcrystallinity in an X-ray diffraction test, while the degree ofamorphousness increased with lower film formation temperature in thecase of those formed at 80° C. or lower.

As is understood from the above results, formation of the transparentconductive layer must be performed at or above a given temperaturedepending on the tin content (to provide crystallinity) in order toreduce R/R₀ in respect of acid resistance, while elevation of the filmformation temperature leads to an increased trend of causing cracking inrespect of acid and alkali resistances. Although an increase in R/R₀ islittle when cracks formed in the transparent conductive layer are fine,even fine cracks cause disconnection of wirings when patterning is somade as to give a fine pattern to the transparent conductive layer(particularly when fine wirings are provided). This will provideinoperative portions in liquid crystal and other display devices with aconductive laminate of the kind as described above. Thus, even finecracks seriously damage conductive laminates in such a case.

Under these circumstances, it would be a great convenience if occurrenceof cracking could be prevented even in the case of higher film formationtemperatures.

Preparatory Test 3

In conductive laminates as shown in FIG. 1, in which ITO was used as thematerial of an intermediate layer 3, examination was made of the tincontent of the intermediate layer at which neither cracking nor peelingin a transparent conductive layer 4 is caused by immersion in an acid.The transparent conductive layer 4 was formed from indium oxide or ITOcontaining 0 to 7 atomic % of tin at a film formation temperature of 90°to 300° C., particularly 100° to 200° C. (100° C. in the case of 0atomic % of Sn, 200° C. in the case of 6 atomic % of Sn). The thicknessof the layer 4 was 400 Å.

The intermediate layer 3 was formed at a film formation temperature of20° to 200° C. (preferably 50° to 100° C.), and had a thickness of 200Å.

Examination was made of the tin content of the intermediate layer atwhich neither cracking nor peeling in the transparent conductive layeris caused with maintenance of R/R₀ ≦2.0 by the same immersion in an acidas in the above-mentioned Preparatory Test 2.

The results are shown in the following Table 3, in which film formingtemperature T_(s) are mentioned together.

                  TABLE 3                                                         ______________________________________                                        Transparent                                                                   conductive layer                                                                              Intermediate layer                                            ______________________________________                                        Sn:     0 at. %     Sn:    7 at. % or more                                    T.sub.s :                                                                             90˜140° C.                                                                   T.sub.s :                                                                            20˜200° C.                                                       preferably 20˜100° C.                 Sn:     1˜2 at. %                                                                           Sn:    8 at. % or more                                    T.sub.s :                                                                             140˜200° C.                                                                  T.sub.s :                                                                            50˜200° C.                                                       preferably 50˜150° C.                 Sn:     5˜7 at. %                                                                           Sn:    10 at. % or more                                   T.sub.s :                                                                             180˜200° C.                                                                  T.sub.s :                                                                            50˜200° C.                            ______________________________________                                    

The following matter can be understood from Table 3. In order to meetthe above-mentioned requirements, the tin content of the intermediatelayer must be higher as the tin content of the transparent conductivelayer is higher, and the tin content of the intermediate layer must bealways higher than that of the transparent conductive layer.

The reasons for this fact is believed to be as follows. With a highertin content in the transparent conductive layer, the temperature offorming the layer must be higher (see the above-mentioned PreparatoryTest 2). Thus, the internal stress setting up in the transparentconductive layer may increase due to a difference in thermal expansioncoefficient between the transparent conductive layer and the substrate.The above-mentioned internal stress can be relaxed by providing anintermediate layer with a further higher tin content between thesubstrate and the transparent conductive layer to prevent cracking orpeeling during immersion in an acid.

Preparatory Test 4

As to conductive laminates 1 as shown in FIG. 1, in which amorphous tinoxide was used as the material of the intermediate layer 3, examinationwas made of a relationship between the thickness of the intermediatelayer and the change R/R₀ in the sheet resistance before and afterimmersion in an acid. The film formation temperature was 200° C. orlower, for example, 100° C. The transparent conductive layer 4 wasformed from indium oxide or ITO containing 0 to 7 atomic % of tin at orabove a necessary film formation temperature as listed in Table 1,particularly at 100° to 200° C. (100° C. in the case of 0 atomic % oftin, 200° C. in the case of 6 atomic % of tin), and had a thickness of400 Å. The R₀ was 400 to 600 Ω/□, and the light transmittance beforeimmersion in an acid was 82 to 75%. The thickness of the layer wasmeasured with a tallystep when it was 300 Å or more, while a smallerthickness was calculated from the rate of evaporation and the time offilm formation (the same will apply in the tests mentioned later).

The test results are shown in FIG. 3.

When the thickness of the intermediate layer was 80 Å or less, the valueof R/R₀ drastically increased. This was caused by formation of manycracks in the transparent conductive layer by immersion in the acid(peeling occurred in some cases).

The value of R/R₀ was 1.4 when the thickness of the intermediate layerwas 80 Å, decreased with an increase in the thickness of theintermediate layer, and reached 1 when the thickness of the intermediatelayer was 500 Å or more. When the thickness of the intermediate layerwas 80 Å or more, no cracks were observed in the transparent conductivelayer.

When the material of the intermediate layer was ITO containing 10 atomic% of tin, substantially the same results were obtained. The intermediatelayer was amorphous in an X-ray diffraction test, while the transparentconductive layer was crystalline.

As is understood from the above results, it is preferred that theintermediate layer be 80 Å or more and amorphous, and that thetransparent conductive layer be crystalline (substantial crystallinityas a whole will suffice even if it may contain some amorphous portions).

Preparatory Test 5

As to conductive laminates 1 as shown in FIG. 1, the transparentconductive layer 4 was formed from indium oxide or ITO containing lessthan 7 atomic % of tin, for example, 6 atomic % of tin, and had athickness of 400 Å. The film formation temperature was 100° to 140° C.in the case of the former and 200° C. in the case of the latter.

The intermediate layer 3 was formed from ITO containing 7 atomic % ormore of tin oxide in this example. Examination was made of arelationship between the thickness of the intermediate layer and thechange R/R₀ in the sheet resistance before and after immersion in a 5wt. % aqueous KOH solution (20° C.) for 10 minutes together withobservation of the surface state. The film formation temperature for theintermediate layer was 20° to 200° C., in this case, 50° to 100° C.

When the transparent conductive layer 4 was formed from ITO containing 6atomic % of tin, the sheet resistance R₀ before immersion in the aqueousKOH solution was 400 to 300 Ω/□, and the light transmittance was 80% orhigher.

The test results are shown in Table 4. In the table, o, Δ, and x standfor the respective states as mentioned below (the same will applyhereinafter).

o: R/R₀ ≦2.0, neither cracking nor peeling was observed.

Δ: R/R₀ ≦2.0, cracking occurred but not peeling was observed.

x: R/R₀ ≦2.0, cracking and peeling occurred.

                  TABLE 4                                                         ______________________________________                                        Thickness of                                                                  intermediate layer                                                                            Rating                                                        (Å)         (alkali resistance)                                           ______________________________________                                         0              x                                                              50             Δ                                                        70             o                                                             100             o                                                             300             o                                                             500             o                                                             700             o                                                             1000            o                                                             ______________________________________                                    

When the thickness of the intermediate layer was 70 Å or more, the valueof R/R₀ was 2.0 or less, and neither cracking nor peeling was observed.

Preparatory Test 6

As to conductive laminates 1 as shown in FIG. 1, in which theintermediate layer 3 was formed from indium oxide, ITO having a variedtin content of 1 to 30 atomic %, or tin oxide at a film formationtemperature of 20° to 200° C. (70° C. in this case), and had a thicknessof 200 Å, a relationship between the tin content of the intermediatelayer 2 and the alkali resistance was examined by conducting the sametest as in the above-mentioned test 5. The sheet resistance R₀ beforeimmersion in an aqueous KOH solution was 400 to 300 Ω/□, and the lighttransmittance was 80% or higher.

The test results are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                        Tin content of                                                                intermediate layer                                                                            Rating                                                        (at. %)         (alkali resistance)                                           ______________________________________                                        0               x                                                             1               x                                                             3               Δ                                                       4               Δ                                                       7               o                                                             10              o                                                             25              o                                                             30              o                                                             tin oxide alone o                                                             ______________________________________                                    

When the tin content of the intermediate layer was 7 atomic % or more,the value of R/R₀ was 2.0 or less, and neither cracking nor peeling wasobserved.

The results of the tests 1 to 6 are summarized as follows.

(a) The acid resistance is improved under the following conditions.

(1) The tin content of the intermediate layer is higher than that of thetransparent conductive layer, and is desirably 7 atomic % or more,preferably 10 atomic % or more.

(2) The thickness of the intermediate layer is 80 Å or more. The filmformation temperature for the intermediate layer has only to be lowerthan a temperature below which the substrate is resistant to thetemperature. In the case of, for example, PES, it has only to be 200° C.or lower.

(3) The tin content of the transparent conductive layer is 10 atomic %or less, preferably 7 atomic % or less.

(4) It is preferred that the film formation temperature for thetransparent conductive layer be higher as the tin content thereof ishigher, and be as listed in Table 1 in accordance with the tin content,provided that it is lower than a temperature below which the substrateis resistant to the temperature. It is 200° C. or lower in the case of,for example, PES.

(b) The alkali resistance is improved under the following conditions.

(5) The same as mentioned in (1) above.

(6) The same as mentioned in (2) above except that the thickness of theintermediate layer is 70 Å or more.

Examples according to the present invention will now be specificallydescribed together with comparative examples.

As to conductive laminates having respective intermediate layers withvarious tin contents between respective substrates and transparentconductive layers, the same acid and alkali resistance tests asdescribed above were conducted.

Using a vacuum evaporation and deposition apparatus as shown in FIG. 4,an intermediate layer and a transparent conductive layer were depositedin sequence on that surface of a PES sheet of 100 μm in thickness havinga water-permeation-proof vinylidene chloride resin layer of 1 to 30 μm,for example, 20 μm, in thickness applied thereon which was remote fromthe water-permeation-proof layer. Thus, a transparent conductivelaminate was prepared.

The vacuum evaporation and deposition apparatus is partitioned intocompartments 30, 31b, 31a, and 32. A wind-up roll 36 and a feed roll 33for a sheet substrate 2 are disposed in the compartments 32 and 30,respectively, on both sides. The substrate 2 is continuously carriedbetween both the rolls while subjecting the same to the followingtreatments.

The sheet substrate 2 is first carried in a zigzag direction over fiveconveyor rollers 26 in the compartment 30 while preliminarily heatingthe same by halogen heater lamps 27 disposed in the zigzags of the sheetsubstrate 2 to remove adsorbed water from the sheet substrate 2,followed by an electric discharge treatment in an electric dischargeapparatus 25 to clean the sheet substrate.

The operation conditions in the compartment 30 are as follows.

Heating temperature: 80° to 150° C.;

Reduced pressure 10⁻⁴ to 10⁻⁵ Torr;

Electric discharge treatment: Gas for use is an O₂ gas, an Ar gas, or anAr+O₂ mixture gas; DC or AC discharge (0 to 1000 W, 0 W standing for noelectric discharge treatment).

The sheet substrate 2 is then carried into the compartment 31b, where avapor generated from an evaporation source 42b was deposited on thesheet substrate 2 maintained at a predetermined temperature by closecontact with a constant-temperature roller 29 (capable of controllingthe temperature at -10° to 250° C.) to form an intermediate layer. Thethickness of the intermediate layer is monitored and controlled by aquartz vibration type film thickness monitor 28. The operationconditions in the compartment 31b are as follows.

Evaporation source 42b: Sn, binary evaporation of Sn and In, SnO₂, orITO containing 7 atomic % or more of Sn;

Heating method: heating with an electron gun (SnO₂ or ITO), resistanceheating (Sn, or binary evaporation of Sn and In);

Gas electric discharge apparatus 37: high-frequency electric discharge(the details will be given later);

Evaporation rate: 100 to 1,000 Å/min;

Oxygen pressure: 5×14⁻⁴ to 3.0×14⁻³ Torr;

High-frequency power: 200 to 800 W (13.56 MHz);

Maintained substrate temperature: 50° to 100° C.

Subsequently, the sheet substrate 2 is carried into the compartment 31ahaving the same structure as that of the compartment 31b, where atransparent conductive layer is formed on the intermediate layer. Theoperation conditions in the compartment 31a are as follows.

Evaporation source 42a: In or ITO containing 10 atomic % or less of Sn;

Heating method: heating with an electron gun or resistance heating;

Electric discharge apparatus 37: the same as mentioned above;

Evaporation rate: 100 to 2,000 Å/min;

Oxygen pressure: 3×10⁻⁴ to 3.0×10⁻³ Torr;

High-frequency power: the same as mentioned above;

Maintained substrate temperature: 90° C. or higher, for example, 130°C., in the case of an evaporation source containing no Sn, 180° C. orhigher, for example, 190° C., in the case of an evaporation sourcecontaining 5 atomic % of Sn, and the same as in the compartment 31b inother cases.

Finally, the sheet substrate 2 is carried into the compartment 32, wherethe sheet resistance is measured between two conveyor rollers 26 with asheet resistance monitor 24 and the substrate is wound up on the wind-uproll 36.

The high-frequency electric discharge apparatuses 37 disposed in thecompartments 31b and 31a will now be illustrated in detail.

As shown in FIG. 5, the electric discharge electrodes are a plurality ofrings 45a and 45b disposed so as to enclose therein the peripheralsurface of a gas (oxygen) feeding tube 43. The whole of the electricdischarge apparatus 37 is wound by a water cooling pipe for cooling theapparatus, not shown in the figure. One ring electrode 45a is connectedthrough a lead wire 67 with a high frequency input terminal 48, whilethe other ring electrode 45b is connected through a lead wire 58 with ametallic deposition-proof member 44 which is connected through ametallic attachment plate 39 with ground. The above-mentioned electrodes45a and 45b consist of, for example, copper, stainless steel or platinumband rings having an inner diameter of 2 to 10 cm and a width of 0.5 to10 cm, which forms a C coupling type (capacity coupling type) ofelectric discharge in the feeding tube 43. The above-mentioned bandrings become to be able to input a strong high frequency power for along time when they are cooled by the cooling pipe wound around theapparatus.

The above-mentioned reactive vacuum evaporation and deposition methodwith the gas electric discharge apparatus 37 is characterized in thefollowing points (1) to (6), as compared with the conventional methods.

(1) Since a reaction gas is activated or ionized by applying ahigh-frequency voltage to the electric discharge apparatus, not only thereactivity of the gas is enhanced to promote the reaction thereof withan evaporated substance, but also the electric discharge electrodes 45can be disposed in positions being out of contact with the dischargingregion in the electric discharge portion of the apparatus. Therefore,the electrodes 45 are not bombarded during discharging so that noelectrode materials are incorporated into the gas. Thus, nocontamination of a deposited film occurs. On the contrary, ifdischarging is performed by applying a DC voltage to the electricdischarge apparatus, the electrodes must be unfavorably disposed incontact with the discharging region.

(2) The disposition of the electric discharge electrodes 45 around theperiphery of the feeding tube 43 can efficiently effectuate ionizationor activation of the gas in the feeding tube 43 keeping the gas pressurehigh without raising the gas pressure in the evaporation space.Accordingly, the amount and rate of the gas being fed can be increased.Since the gas pressure can be reduced in the evaporation space, fieldacceleration of the evaporated substance becomes unnecessary.Accordingly, not only metals but also oxides can be used as the materialto be evaporated, thus expanding the scope of the material to be chosen.Besides, the material of the substrate to be subjected to deposition canbe selected from among a wide variety of materials. Thus, formation of agood-quality deposited film is possible. The scope of the substratetemperature to be chosen is expanded, thus facilitating heating andcooling of the substrate.

(3) Since the gas discharging region is limited in the feeding tube 43and hence separated from the electrodes 45, bombardment of theelectrodes with gas ions generated during discharging can be prevented.Thus, evaporation of the electrode materials due to heating andbombardment thereof can be prevented so that contamination of theevaporation space can be prevented.

(4) Since the deposition-proof members 44 and 46 are so disposed as toenclose therein the feeding tube 43 and the electrodes 45, not onlyadhesion of the evaporated substance to the feeding tube 43, electrodes45, and high-frequency input terminal 48 can be prevented, but alsoleakage of high-frequency power through the attachment plate 39, theelectrodes 45, and the feeding tube 43 can be effectively prevented tosecure stable electric discharge.

(5) Since the gas electric discharge apparatus 37 can be attached in abell jar with an installing bed by means of a simple structure,attachment and detachment works can be facilitated. When film formationis performed on a substrate having a large area, the positions andnumber of electric discharge apparatuses can be so optimized byadjustment as to secure uniform film formation. For example, theelectric discharge apparatuses can be set in an adequate position(s), ora plurality of discharge apparatuses can be set for the purpose ofuniform film formation.

(6) Since the direction of orientation of a gas release opening can beeasily changed, electric discharge without disorder can be secured evenif the rate of evaporation varies. Particularly when the gas electricdischarge apparatus is so set that the gas release opening does notorient somewhere between the evaporation source and the substrate,electric discharge can be continued stably to attain homogeneity in thequality of the deposited film.

(7) When the attachment bed, the electric discharge electrodes 45, andthe deposition-proof member 44 are cooled with water, superheatingduring discharging can be prevented so that a strong high-frequencypower can be input to promote the reactive vacuum evaporation anddeposition.

Thus, a number of transparent conductive laminates having theinteremediate layer 3 and the transparent conductive layer 4 depositedin sequence on one surface of the substrate 2 and thewater-permeation-proof layer 5 formed on the other surface of thesubstrate as shown in FIG. 6 were obtained.

Examination was made of not only the sheet resistance and lighttransmittance but also the same acid and alkali resistances of eachobtained transparent conductive laminate each time it was subjected tothe operation conditions in the compartment 31b or 31a.

The results are exemplified in the following Table 6, in which Ts and RFstand for the maintained substrate temperature and the high frequencypower, respectively.

                                      TABLE 6                                     __________________________________________________________________________    Transparent                                                                   conductive                                                                              Intermediate layer                                                                            Acid Alkali                                         No.                                                                              layer  Sn content                                                                           Ts       resistance                                                                         resistance                                                                         Remarks                                   __________________________________________________________________________    1  Sn: 0 at. %                                                                          ≧ 7                                                                       at. %                                                                             150° C. or lower                                                                o    o    Ex.                                       2  Ts: 90˜                                                                        0  at. %                                                                             100° C.                                                                         Δ                                                                            x    Comp. Ex.                                 3  150° C.                                                                       7  at. %                                                                              50° C.                                                                         o    o    Ex.                                       4         1  at. %                                                                             170° C.                                                                         Δ                                                                            x    Comp. Ex.                                 5  Sn: 1 at. %                                                                          ≧ 10                                                                      at. %                                                                             160° C. or lower                                                                o    o    Ex.                                       6  Ts: 130˜                                                                       0  at. %                                                                              90° C.                                                                         Δ                                                                            Δ                                                                            Comp. Ex.                                 7  165° C.                                                                       2  at. %                                                                             160° C.                                                                         Δ                                                                            x    Comp. Ex.                                 8         20 at. %                                                                              50° C.                                                                         o    o    Ex.                                       9  Sn: 5 at. %                                                                          ≧ 20                                                                      at. %                                                                             180° C. or lower                                                                o    o    Ex.                                       10 Ts: 150˜                                                                       0  at. %                                                                             130° C.                                                                         Δ                                                                            x    Comp. Ex.                                 11 180° C.                                                                       5  at. %                                                                             180° C.                                                                         Δ                                                                            x    Comp. Ex.                                 12        SnO.sub.2                                                                            100° C.                                                                         o    o    Ex.                                                 ≧ 30                                                                      at. %                                                            13 Sn: 7 at. %                                                                          ≧ 20                                                                      at. %                                                                             190° C. or lower                                                                o    o    Ex.                                       14 Ts: 170˜                                                                       0  at. %                                                                             110° C.                                                                         x    x    Comp. Ex.                                 15 190° C.                                                                       SnO.sub.2                                                                             50° C.                                                                         o    o    Ex.                                                 ≧ 30                                                                      at. %                                                            __________________________________________________________________________

Of these conductive laminates, those excellent in both acid and alkaliresistances are conductive laminates Nos. 1, 3, 5, 8, 9, 12, 13, and 15having a tin content of 7 atomic % or more in their intermediate layers,which were confirmed to be amorphous as a result of an X-ray diffractiontest conducted just as they were formed. The intermediate layers of theother conductive laminates were found to contain crystalline portions.

When intermediate layers having the same composition as in theabove-mentioned laminates Nos. 1, 5, 9, and 13 were formed attemperatures higher than the film formation temperatures listed in Table6, crystalline portions were included in the intermediate layers, andconductive laminates each formed by depositing thereon a transparentconductive layer were observed to give rise to cracking and/or peelingin the transparent conductive layer when immersed in either an acid oran alkali. The same phenomenon was observed when the tin contents of theintermediate layers were decreased in those corresponding to theabove-mentioned laminates Nos. 1, 5, 9, and 13 though the film formationtemperatures therefor were the same as in the above-mentioned laminates.

It is understood from the above results that the intermediate layer ismore apt to become amorphous as the tin content of the intermediatelayer is higher and as the film formation temperature for theintermediate layer is lower, leading to improvements in the acid andalkali resistances of a conductive laminate comprising therein theintermediate layer.

This is belived to be due to the following reasons. (1) As the filmformation temperature is lower, the deposited layer is more easilyquenched due to absorption of its heat by the substrate during vacuumevaporation and deposition to tend to become amorphous. (2) As the tincontent of the ITO-deposited layer is higher, the intermediate layertends to become amorphous. (3) Therefore, as the tin content of theITO-deposited layer is higher, the upper limit of the film formationtemperature at which amorphousness can be secured is higher.

When an amorphous intermediate layer was formed from silicon oxide(SiO₂) or aluminum oxide (Al₂ O₃) at a film formation temperature of150° C. or lower for the former or 170° C. or lower for the latteraccording to reactive vacuum evaporation and deposition or reactivesputtering, a conductive laminate formed by forming thereon atransparent conductive layer also showed excellent acid and alkaliresistances like the above-mentioned examples.

An example of a liquid crystal display formed by effecting patternetching of the transparent conductive and intermediate layers of theconductive laminate according to the present invention in apredetermined pattern is shown in FIG. 7.

The liquid crystal display 9 comprises transparent conductive laminates1 having an intermediate layer 3 and a transparent conductive layer 4deposited in sequence with patterning on a transparent substrate 2, thetransparent conductive layers of which confront with each other, andwhich sandwich a liquid crystal 6 via orientation films 7. Awater-permeation-proof layer 5 and a polarizing filter 8 are provided insequence on the outer side of each transparent substrate 2.

The conductive laminate according to the present invention can besuitably used in various display devices such as not only a liquidcrystal display device but also electroluminescence, electrochromic, andfluorescence display devices.

Industrial Applicability

As described above, since the conductive laminate according to thepresent invention has a structure comprising a substantially amorphousintermediate layer or an intermediate layer capable of providingchemical resistance to a transparent conductive layer between asubstrate and the transparent conductive layer, the acid and alkaliresistance of it are high. When the laminate is used in, for example, aliquid crystal display, neither cracking nor peeling in the surfaceportion of the laminate occurs even if it was washed with an alkali inthe post-treatment of patterning to remove a resist, or even if it iswashed with an acid to clean the surface of the transparent conductivelayer. Thus, it can be used with sufficient reliability.

We claim:
 1. A conductive laminate characterized by providing insequence an intermediate layer made of an amorphous metallic oxide or anamorphous semi-metallic oxide and a transparent conductive layer made ofa crystalline metal or a crystalline metallic oxide on a transparentsubstrate.
 2. A conductive laminates as claimed in claim 1, wherein thematerial of said conductive layer is a member selected from among Au,Pd, Cr, Ni, SnO₂, In₂ O₃, ZnO, TiO₂, CdO, CdO-SnO₂, and ITO.
 3. Aconductive laminate as claimed in claim 1, wherein the material of saidintermediate layer is a member selected from among SnO₂, ITO, SiO₂, andAl₂ O₃.
 4. A conductive laminate as claimed in claim 1, wherein saidconductive layer is made of In₂ O₃ or ITO having a tin content of lessthan 7 atomic %, and said intermediate layer is made of ITO having a tincontent of 7 atomic % or more or SnO₂.
 5. A conductive laminate asclaimed in claim 4, wherein the tin content of ITO in said intermediatelayer is 10 atomic % or more.
 6. A conductive laminate as claimed inclaim 1, wherein the thickness of said conductive layer is 200 to 10,000Å.
 7. A conductive laminate as claimed in claim 1, wherein the thicknessof said intermediate layer is 80 to 300 Å.
 8. A conductive laminate asclaimed in claim 1, wherein the material of said substrate is a memberselected from among inorganic materials such as quartz glass, sodaglass, potassium glass, and other glass; and organic polymer materialssuch as polyethylene terephthalate (PET), polyethylene naphthalate,polyhexamethylenediamide, poly-γ-butyramide, poly-m-xylenediamineterephthalamide, aromatic polyesters or aromatic polyester carbonatesprepared mainly from bisphenol A, its halogenated derivative and an acyldichloride, polyamide copolymers of m-phenylenediamine, isophthalic acidand terephthalic acid, polycarbonate, polypropylene, polyimides,polyamides, imido-polybenzimidazole, polyethersulfone PES), polyetherether ketone, polysulfone, polyether imide, and triacetylcellulose.